How is the amount of liquefied gas remaining in a cylinder determined?

To determine the amount of liquefied gas remaining in a cylinder, the most reliable method is to measure the weight of the cylinder. When the cylinder is filled with liquefied gas, it will have a specific weight that can be compared to its empty weight (tare weight) to establish how much gas is inside. This method is particularly effective because it provides a direct measure of the contents rather than relying on external factors, such as pressure or temperature, which can vary based on environmental conditions.

While the volume of the cylinder is fixed, it does not indicate the amount of gas remaining because the liquid gas can fill varying portions of the cylinder, depending on how much has been used. Pressure readings might indicate how much gas is in a gaseous state or provide some information about the contents, but these can also be misleading, as the pressure inside a cylinder can fluctuate with temperature changes or due to the phase of the gas. Lastly, temperature is another factor that affects the pressure of gases but does not provide a direct measure of the remaining liquid gas. Thus, using weight offers a definitive approach to gauge the remaining liquefied gas accurately.